Understanding the mechanisms underlying heterogeneous genomic divergence is of particular interest in evolutionary biology. Highly differentiated genomic regions, known as genomic islands, often evolve between diverging lineages. These genomic islands may be related to selection promoting adaptation or reproductive isolation. Based on whole genome assembly and genome-wide RAD sequencing in a pair of yellow croakers (genus: Larimichthys), we investigated the evolutionary processes shaping genomic landscapes of divergence. Demographic modelling indicated that the two species diverged following a secondary contact scenario, where differential introgression and linked selection were suggested to be involved in heterogeneous genomic divergence. We identified reduced recombination rate in genomic islands and a relatively good conservation of both genetic diversity and recombination landscapes between species, which highlight the roles of linked selection and recombination rate variation in promoting heterogeneous divergence in the common ancestral lineage of the two species. In addition, we found a positive correlation between differentiation (F-ST) and absolute sequence divergence (D-xy), and elevated D-xy in genomic islands, indicating that the genomic landscape of divergence was not shaped by linked selection alone. Restricted gene flow in highly differentiated regions has probably remodelled the landscape of heterogeneous genomic divergence. This study highlights that highly differentiated genomic regions can also arise from a combination of linked selection and differential gene flow in interaction with varying recombination rates.

Pseudocaranx dentex (white trevally) which belongs to the Carangidae family, is an important commercial fishery and aquaculture resource in Asia. However, its evolution and population genetics have received little attention which was limited by the mitogenome information absence. Here, we sequenced and annotated the complete mitochondrial genome of P. dentex which was 16,569 bp in length, containing twenty-two tRNAs (transfer RNAs), thirteen PCGs (protein-coding genes), two rRNAs (ribosomal RNAs), and one non-coding region with conservative gene arrangement. The Ka/Ks ratio analysis among Carangidae fishes indicated the PCGs were suffering purify selection and the values were related to the taxonomic status and further influenced by their living habits. Phylogenetic analysis based on the PCGs sequences of mitogenomes among 36 species presented three major clades in Carangidae. According to the phylogenetic tree, we further analyzed the taxonomic confusion of Carangoides equula which was on the same branch with P. dentex but a different branch with Carangoides spp. We inferred Kaiwarinus equula should be the accepted name and belong to the independent Kaiwarinus genus which was the sister genus of Pseudocaranx. This work provides mitochondrial genetic information and verifies the taxonomic status of P. dentex, and further helps to recognize the phylogenetic relationship and evolutionary history of Carangidae.

Crustaceans are important food sources worldwide and possess significant ecological status in the marine ecosystem. However, our understanding of the diversity and evolution of RNA viruses in crustaceans, especially in economic crustaceans, is still limited. Here, 106 batches of economic crustaceans including 13 species were collected from 24 locations in China during 2016–2021. We identified 90 RNA viruses, 69 of which were divergent from the known viruses. Viral transcripts were assigned to 18 different viral families/clades and three unclassified groups. Among the identified viruses, five were double-stranded RNA viruses, 74 were positive-sense single-stranded RNA (+ssRNA) viruses, nine were negative-sense single-stranded RNA (−ssRNA) viruses, and two belonged to an unclassified RNA virus group. Phylogenetic analyses showed that crustacean viruses were often clustered with viruses identified from invertebrates. Remarkably, most crustacean viruses were closely related to those from different host species along the same food chain or ecological aquatic niche. In addition, the genome structures of the newly discovered picornaviruses exhibited remarkable diversity. Our study significantly expands the diversity of viruses in important economic crustaceans and provides essential data for the risk assessment of the pathogens spreading in the global aquaculture industry. IMPORTANCE: The study delves into the largely uncharted territory of RNA viruses in crustaceans, which are not only vital for global food supply but also play a pivotal role in marine ecosystems. Focusing on economic crustaceans, the research uncovers 90 RNA viruses, with 69 being potentially new to science, highlighting the vast unknown viral diversity within these marine organisms. The findings reveal that these viruses are often related to those found in other invertebrates and tend to share close relationships with viruses from species within the same food web or habitat. This suggests that viruses may move between different marine species more frequently than previously thought. The discovery of such a wide variety of viruses, particularly the diverse genome structures of newly identified picornaviruses, is a significant leap forward in understanding the crustacean virology. This knowledge is crucial for managing disease risks in aquaculture and maintaining the balance of marine ecosystems.